Admission control of emergency connections

ABSTRACT

Emergency or prioritized communications in a wireless communication network are handled during negotiation of access to the wireless communication network from a mobile station using dedicated emergency multiple-access sequences which are also used as communication division codes in communication with a base station of the network.

PRIORITY APPLICATIONS

This application is a continuation application claiming priority fromU.S. application Ser. No. 12/674,978, filed Feb. 24, 2010, which is theU.S. national phase of International Application No. PCT/EP2007/058801filed 24 Aug. 2007, which designated the U.S., the entire contents ofeach of which are hereby incorporated by reference.

TECHNICAL FIELD

The technology relates to emergency or prioritized communication in atelecommunications network and in particular to setting up acommunication link for emergency or prioritized communication.

BACKGROUND

The setup of traffic connections for the air interface in a telecomsystem is traditionally handled by a specific node BSC for GSM, RNC forUMTS, and ASN-GW for an IEEE802.16/WiMAX network. The setup of a serviceis typically requested by a mobile station (MS) and signaled to anapplication server in the core network.

However in a loaded network, it may be difficult for the MS to getaccess to air interface resources even to request the setup of aservice. In case the service is needed for emergency purposes, i.e. 911there is a strong wish to be able to prioritize this request andminimize the latency for setup of such services.

The IEEE802.16 has support for different QoS, which can have differentpriority settings. However before a setup of a service is possible tomake the MS must be authenticated and admitted to the network.

Also as IEEE 802.16 is an OFDMA based system where all air interfaceresources are shared between users a mobile station (MS) may encounterproblems to be granted bandwidth to request the setup of a service ifthe air interface is fully utilized and as there today exist nopossibility to differentiate different users during initial ranging orbandwidth request.

SUMMARY

It is therefore an object to remedy at least some of the problemsrelating to known solutions. This is provided in a number of aspects inwhich a first is a method of handling emergency communication between amobile station, MS, and a base station, BS, comprising the steps of:

-   -   initiating an emergency communication link;    -   obtaining specific emergency communication establishment        sequences;    -   using the specific emergency communication establishment        sequences during negotiation of access to the BS;    -   wherein the sequences are also used as communication division        codes.

Specific CDMA codes may be used to indicate emergency access.

The MS may send a second indication of emergency access in anidentification message.

Specific random access preamble sequences may be used to indicateemergency access.

The method may further comprise a step of receiving emergency sequencesfrom the BS.

The method may further comprise a step of reading stored pre setemergency sequences in the MS.

The step of obtaining emergency sequences may comprise a step ofchoosing the sequence randomly from a set of available emergencysequences.

The step of using the sequences during negotiation may be performedduring initial access establishment and/or during negotiation duringbandwidth establishment.

In another aspect, a mobile station for a wireless communication networkis provided, comprising:

-   -   an transceiver for wireless communication with a base station,        i.e. BS;    -   a processor arranged to execute functions for:        -   initiating an emergency communication link;        -   obtaining specific emergency communication establishment            sequences;        -   using the specific emergency communication establishment            sequences during negotiation of access to the BS;    -   wherein the sequences are also used as communication division        codes.

In yet another aspect of the present invention, a base station isprovided for wireless communication with a mobile Station, i.e. MS,comprising means for detecting communication establishment sequences,means for identifying specific emergency sequences from theestablishment sequences, and means for handling emergency communication,wherein the sequences are also used as communication division codes.

Still another aspect of the present invention, a computer program isprovided for a mobile station, i.e. MS, comprising instruction sets for:

-   -   controlling wireless communication with a base station, i.e. BS;    -   initiating an emergency communication link;    -   obtaining specific emergency communication establishment        sequences;    -   using the specific emergency communication establishment        sequences during negotiation of access to the BS;    -   wherein the sequences are also used as communication division        codes.

Usage of standardized/specific multiple-access sequences only allowedfor emergency purposes are proposed to ensure priority of emergencysetups.

A specific parameter is suggested to be included for a number of callmanagement messages for fast detection of emergency calls and thus givethe base station (system) the possibility for prioritization of therequested traffic during admission control to the system.

Handling of emergency calls are enhanced as the probability ofsuccessful setup is increased, which is very much desired in atelecommunication system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates schematically a network;

FIG. 2 illustrates schematically in a block diagram a flowchart of amethod;

FIG. 3 illustrates schematically a situation for two mobile stationsconnecting simultaneously to a base station;

FIG. 4 illustrates schematically in a block diagram a mobile device; and

FIG. 5 illustrates schematically in a block diagram an infrastructuredevice.

DETAILED DESCRIPTION OF NONLIMITING EXAMPLE EMBODIMENTS

In FIG. 1 reference numeral 1 generally indicate a network configurationaccording to the present invention, comprising a base station BS) 5 orsimilar network access gateway for accessing from a mobile station (MS)(which can be any type of wireless terminal, including but not limitedto, e.g. a mobile phone, laptop, PDA (Personal Digital Assistant),security appliance, and so on) 2, 3 to a communication network 6. The MScommunicates wirelessly 4 with the BS 5 using any suitable protocol andradio link. The technology described in this application addresses theproblem when an MS tries to connect to a communication network undercertain circumstances where there is a need to increase the probabilityto actually get a connection: for instance when there is an emergencysituation and there is a need to communicate with an emergencyorganization 7 (e.g. police, fire brigade, and medical help), connectionof alarm equipment, and/or surveillance equipment to a central receivingfacility 7. These circumstances will be discussed further in thisdocument.

The wireless link between the MS and the BS may be of any suitable typeinvolving some means for registration of the MS, including but notlimited to any version of IEEE 802.11, 802.15, 802.16, 802.20, and802.22 series of communication standards and variations thereof (e.g.WiFi, WiMAX, and Wibro), LTE (Long term evolution) in 3GPP, or similarcommunication systems. WiMAX has means for registering the MS using aranging function at early stages of connection establishment and in thatprocess using CDMA codes for random access and in LTE there is a RandomAccess (RA) preamble/response function used in establishment of the MS.In WiMAX specific ranging CDMA codes may be used for alerting thenetwork about the emergency and/or prioritized link and in LTE specificRA preamble sequences may have corresponding function. CDMA codes inWiMAX and preamble sequences in LTE are two examples of multiple-accesssequences. These multiple-access sequences may be orthogonal ornon-orthogonal as understood by the skilled person.

Multiple-access sequences are used to distinguish communication linksfrom each other when all users within a communication cell communicateon the same frequency range and encode information to be transmittedwith a pseudo-random digital sequence unique for each user in the cell(or unique for each thread set up; a user may have several threads openat the same time depending on communication configuration)

It should be noted that the communication link between the BS and thenetwork may be of any suitable kind including either a wired or wirelesslink. The link may use any suitable protocol depending on type and levelof layer (e.g. as indicated by the OSI model) as understood by theperson skilled in the art.

The BS may be alerted about the level of emergency or level of prioritydesired using different ways depending on type of connection, type ofcommunication protocol, and level of connection already established:

1. If the MS has not been connected yet, establishment sequencesspecifically agreed upon as emergency sequences may be used.

2. If the MS is connected but has not been granted bandwidth it may alsouse emergency sequences.

3. If connection and bandwidth has been negotiated about, informationelements in call management messages may be used to alert the BS aboutthe emergency connection.

An overall flowchart for handling of emergency calls is shown in FIG. 2:

201. A decision to connect to a service is taken in first step.

202. It is checked if the MS is registered in the network.

203. If it is registered it is checked if the MS has been grantedbandwidth.

204. If it has been granted bandwidth call management messages withemergency information elements are used.

205. If the MS is not registered emergency random access operation isused.

206. If the MS is registered but has not yet been granted bandwidth,emergency bandwidth request is used.

Each of the involved processes is described in the sections below.

MS requests setup of emergency call

When a user or a machine determines that there is a need forestablishing a contact with a receiving service, the MS is initiated toconnect to the network 6. Typically this is done by a user dialing 112,911, or some other emergency call number (depending on type of emergencyand/or country); however, the MS may be arranged to be informed aboutthe emergency number to be used where the connection is to beestablished). However, this could also be a connection from a machine ina system which is capable of automatically determining that a connectionis to be started, e.g. a by authorities and operators approvedsurveillance camera automatically requesting to start sending data orvideo upon an alarm or triggering event. The receiving service can be anemergency center 7 directing the call to suitable service needed(police, ambulance services and so on) or it may be a security centerreceiving for instance a distress alarm or burglar alarm signal.Similarly the receiving service may be part of a surveillance system forelderly or handicapped people, e.g. in relation to home care services,where the person under care can contact the home care system for generalhelp or help in a distress situation. There are today many solutionswhere an elderly or handicapped person has a personal alarm in the formof an arm wrist device with a distress call button. This arm wristdevice may be arranged to communicate with a distress call center usinga communication protocol compatible with the technology described inthis application. Similarly, surveillance cameras and similar devicesmay be arranged to use a communication protocol compatible with thetechnology described in this application and arranged to transmit imagesto a central storage or handling center if a triggering event hasoccurred, for instance a motion detection event (internally in thecamera as a software detector using the images or an external dedicatedmotion detector).

When pushing the call setup button or initiating the connection in anyother suitable manner, the MS will start to request the setup of atransport connection or activate a pre-setup connection to carry therequested service.

The MS can be in different states and will perform different operationsdepending on its current state in the system:

-   -   Normal/active registered in the system with active services.    -   Normal/active registered in the system with no active services    -   Idle and not registered or even belonging to the system. Idle in        this context is interpreted as not connected to the current BS.        The MS may be registered in a core network (or ASN-GW in the        WiMAX case).        MS is registered in the system and has granted UL bandwidth.

This is a typical case if the terminal or device already is activeperforming other tasks, such as transferring data files etc. It may thenuse the already granted UL bandwidth for the request of an additionalservice for the emergency purpose.

In the IEEE802.16 this is typically done by sending a dynamic serviceflow addition request message (DSA-REQ). In this message a number ofparameters are set among these are QoS parameter set type, schedulingservice type and traffic priority. Depending on the previousauthentication of the user the operator may allow/set these parametersdifferently.

A generic parameter (e.g. a TLV-coded information element in theIEEE802.16 standard), may be added to control communication, which maybe optionally included to call management messages indicating that theseare emergency related.

Examples of IEEE802.16 messages where an emergency parameter havebenefit are:

1. DSA-REQ/RSP

2. DSC-REQ/RSP

The BS (system) may also use this information for prioritizing of thisconnection for further data transfer, i.e. enhancing the probability forthe specific communication data to be delivered to the final destinationand granting access to the network.

MS is registered in the system but need UL bandwidth.

In this case the MS needs to perform random access in order to requestbandwidth (BW). To improve both the probability of a successful requestof BW as well as minimize the latency for grant of BW for ULtransmission it is proposed to have separate multiple-access sequencesallocated for BW-request for emergency purposes.

It may be relevant to add emergency parameters in any subsequentmanagement messages (e.g. DSA-REQ/RSP and DSC-REQ/RSP for IEEE802.16).

MS is not registered in the system.

In this case the MS is not registered in a system. This can be due tolack of roaming agreement with a system (visited NW) where it hascoverage or due to admission control rejection from its own NW (fullnetwork). Specified multiple-access sequences also for initial randomaccess will then improve the setup of emergency connections as admissioncontrol functionality may be adjusted for this purpose.

The emergency parameter described earlier may be added to additionalIEEE802.16 messages used for network entry below:

1. RNG-REQ/RSP

2. SBC-REQ/RSP

3. PKM-REQ/RSP

4. REG-REQ/RSP

5. DSA-REQ/RSP

In this case authentication processes may be simplified or omitted andthe MS is allowed to enter the system.

Static or dynamic information transfer of emergency sequences.

Two methods for determining specific multiple-access sequences for useare proposed.

1. Static specification by reserving a limited number of multiple-accesssequences in the standard. This method is very simple and ensures simpleinteroperability between different manufacturers and system vendors. Themultiple-access sequences are then known to the MS and stored in amemory of the MS.

2. Dynamic specification by broadcast information. Two new groups ofmultiple-access sequences for emergency initial random access andemergency BW request are added to the specification and broadcasted in asimilar way as CDMA codes for initial ranging, BW request, periodicranging, and handover are signaled today for IEEE802.16. By this methodit is possible for the system to increase the number of multiple-accesssequences for emergency purposes dynamically so that the case when manyMSs (wireless terminals, cameras, etc) need access to the systemsimultaneously may be taken care of without the collision probabilitybeing higher for emergency calls than for normal calls.

The system may by this method even be solely dedicated for authoritydevices for public safety purposes as no multiple-access sequences fornormal operation are sent.

The probability of successful reception is increased as the collisionrisk is decreased. FIG. 3 illustrates this situation; two mobilestations 2, 3 simultaneously try to connect to a common base station 5.Collision risk of UL BW request ranging can be reduced if dedicatedmultiple-access sequences are used solely for emergency purposes. Forinstance, if a first MS (A) 2 need to make an emergency BW request itmay use a sequence 4 different from a second MS (B) 3 sequence 4′ usedfor regular connection purposes. The probability for both MS A and MS Bis in need of an emergency connection is low. However, in order toreduce the problem of two MS doing emergency connection at the sametime, each MS may choose randomly an emergency sequence from a fixed setof available emergency sequences. This would reduce the risk of two MSat the same cell using the same emergency sequence and thus reduce therisk of collision. This may be used in any of the situations asdescribed in this document.

The technology described in this application may be used in connectingmobile stations 2, 3 during emergency or other prioritized events. Sucha mobile station 400 is shown in FIG. 4. The solution may be implementedin software run in a processing unit 401 and stored in a memory 402.Furthermore, the mobile station may comprise an interface 403 forconnecting the processing unit 401 with other components of the mobilestation as understood by the person skilled in the art. Furthermore, themobile station comprises a communication interface 404 for wirelesscommunication with the BS 5. The processing unit 401 may comprise anysuitable computational unit such as but mot limited to a microprocessor,FPGA (Field Programmable Gate Array), ASIC (Application SpecificIntegrated Circuit), or similar units. The mobile station comprises atleast one memory 402 of volatile and/or non-volatile type. The memorymay be for instance a RAM, DRAM, ROM, EEPROM, Flash memory, hard disk,and so on as understood by the skilled person. The communicationinterface may be any suitable as discussed earlier using a code divisionprotocol.

In the solution, the BS device 5 has functionality for detecting andunderstanding these emergency or priority multiple-access sequences.Such a device 500 is shown in FIG. 5. The device 500 comprises also aprocessing unit 501, at least one memory 502, and an interconnectioninterface 503 for connecting to other components (not shown) of the BS5. Furthermore, the device 500 may comprise a downlink communicationinterface 504 and an uplink communication interface 505. The downlinkcommunication interface is arranged to communicate with the mobilestations (directly or indirectly using further downstream infrastructuredevices (not shown)) and the uplink interface 505 is arranged tocommunicate with the communication network. The downlink and uplinkcommunication interfaces may be built into the same physical interfacein some application configurations.

It should be noted that with the term base station is meant an entitythat receives or transmits wireless communication between wirelessterminals and a communication network. This may include for instance abase station in cellular mobile phone networks, an access point orgateway in a Wireless Local Area Network (WLAN), or similar networkaccess gateway devices.

It should be noted that the word “comprising” does not exclude thepresence of other elements or steps than those listed and the words “a”or “an” preceding an element do not exclude the presence of a pluralityof such elements. It should further be noted that any reference signs donot limit the scope of the claims, and that several “means”, “units” or“devices” may be represented by the same item of hardware, and that atleast part of the technology described in this application may beimplemented in either hardware and/or software controlled hardware.

The above mentioned and described embodiments are only given as examplesand should not be limiting. Other solutions, uses, objectives, andfunctions within the scope of the claims should be apparent for theperson skilled in the art.

DEFINITIONS AND ABBREVIATIONS

ASN-GW Access service network gateway

BS Base Station

BSC Base station controller

BW Bandwidth

CDMA Code division multiple access

DSA Dynamic Service flow Addition

DSC Dynamic Service flow Change

IEEE Institute of Electrical and Electronics Engineers

NW Network

OFDMA Orthogonal frequency division multiple access

PKM Privacy Key Management

QoS Quality of service

REG Registration

REQ Request

RNC Radio network controller

RNG Ranging

RSP Response

SBC SS Basic Capabilities

SS Subscriber Station

TLV Type, Length, Value

UL Uplink

1. A method of controlling a wireless terminal, the method comprising:receiving data specifying a group of multiple-access sequences reservedfor prioritized communications, wherein the number of multiple-accesssequences in the group of multiple-access sequences reserved forprioritized communications varies dynamically; and transmitting arequest for establishment of a prioritized communication in which atleast one multiple-access sequence in the group is used to indicate thepriority of the request.
 2. A method according to claim 1, wherein thegroup comprises at least one multiple-access sequence reserved forprioritized initial random access.
 3. A method according to claim 2,wherein the request is for initial random access and wherein the atleast one multiple-access sequence reserved for prioritized initialrandom access is used to indicate the priority of the request forinitial random access.
 4. A method according to claim 1, wherein thegroup comprises at least one multiple-access sequence reserved forrequesting additional bandwidth.
 5. A method according to claim 4,wherein the request is for additional bandwidth and wherein the at leastone multiple-access sequence reserved for additional bandwidth is usedto indicate the priority of the request for additional bandwidth.
 6. Amethod according to claim 1, wherein at least some of themultiple-access sequences comprise CDMA codes.
 7. A method according toclaim 1, wherein at least some of the multiple-access sequences comprisepreamble sequences.
 8. A method according to claim 1, wherein saidreceiving comprises: receiving data specifying a group having a firstnumber of multiple-access sequences reserved for prioritizedcommunications; and receiving data specifying a group having a second,different number of multiple-access sequences reserved for prioritizedcommunications.
 9. A method according to claim 1, comprising encodingthe request with the at least one multiple-access sequence.
 10. A methodof controlling a network access gateway, the method comprising:transmitting data specifying a group of multiple-access sequencesreserved for prioritized communications, wherein the number ofmultiple-access sequences in the group of multiple-access sequencesreserved for prioritized communications varies dynamically; andreceiving a request for establishment of a prioritized communication inwhich at least one multiple-access sequence in the group is used toindicate the priority of the request.
 11. A method according to claim10, wherein the request is encoded using the at least onemultiple-access sequence and wherein the method comprises decoding therequest using the at least one multiple-access sequence.
 12. A methodaccording to claim 10, wherein said transmitting comprises broadcastingdata specifying the group.
 13. A method according to claim 10,comprising increasing the number of multiple-access sequences in thegroup in response to determining an increased need for network accessvia the network access gateway.
 14. A wireless terminal configured to:receive data specifying a group of multiple-access sequences reservedfor prioritized communications, wherein the number of multiple-accesssequences in the group of multiple-access sequences reserved forprioritized communications varies dynamically; and transmit a requestfor establishment of a prioritized communication in which at least onemultiple-access sequence in the group is used to indicate the priorityof the request.
 15. A network access gateway configured to: transmitdata specifying a group of multiple-access sequences reserved forprioritized communications, wherein the number of multiple-accesssequences in the group of multiple-access sequences reserved forprioritized communications varies dynamically; and receive a request forestablishment of a prioritized communication in which at least onemultiple-access sequence in the group is used to indicate the priorityof the request.